1. Field of the Invention
The present invention relates to a current measurement circuit used for evaluating/testing characteristics of, for example, an IC (integrated circuit) tester and also to an apparatus including the current measurement circuit.
2. Description of the Related Art
Examples of known circuits for switching current ranges using relay switches include a circuit disclosed in Japanese Unexamined Patent Application Publication No. 5-119110 (Document 1). The circuit switches a current range resistor 15 using a semiconductor switch, such as a CMOS 32 illustrated in FIG. 1 in this document. Such a semiconductor switch is low in cost compared to mechanical relays (or reed relays) illustrated in FIG. 1 in U.S. Pat. No. 5,994,947 (Document 2), which predates Document 1.
Although such a semiconductor switch is relatively inexpensive, it has a large amount of leakage current and shows somewhat inferior performance compared to mechanical switches.
To overcome such drawbacks, FIG. 2 of Document 2 illustrates a circuit that uses both relays and a semiconductor switch, such as an FET (field effect transistor). The circuit includes three relays (36, 42, and 46 in FIG. 2 in Patent Document 2), two diodes (38 and 40), one buffer (44), and two resistors (34 and 48).
However, the circuit configuration in FIG. 2 of Document 2 requires an increased number of components in order to overcome the drawbacks of degraded measurement accuracy due to leakage if the semiconductor switch is used. Thus, the cost required for the circuit configuration still remains high.